Advice please about Avast Antivirus.

I am a complete novice, and have an old (very slow) 2nd hand computer with windows 98 but no disc.I have downloaded the trial version of Zone alrm and have just downloaded Avast Antivirus, as I had problems downloading AVG free edition,I ticked the box not to change my Outlook Express settings, as I was n`t certain how to set it up so I could still get my email, if my settings were changed.Will the Antivirus programme still work? or do I need to do anything Else?If anyone is kind enough to answer, please go easy on the technical terms, as I am still learning !.Many thanks.

You read me right Granny, avast! can be fine tuned when you want, but the default settings are very good, and it's highly automated.

The best indicator is down on the taskbar, if avast! is working correctly a new icon will appear on the taskbar while e-mail is downloaded, it's an envelope with a blue light in front of it. It appears only as the mail is scanned and then disappears.